کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2487692 1114428 2007 17 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Dielectric Relaxation and Crystallization of Ultraviscous Melt and Glassy States of Aspirin, Ibuprofen, Progesterone, and Quinidine
موضوعات مرتبط
علوم پزشکی و سلامت داروسازی، سم شناسی و علوم دارویی اکتشاف دارویی
پیش نمایش صفحه اول مقاله
Dielectric Relaxation and Crystallization of Ultraviscous Melt and Glassy States of Aspirin, Ibuprofen, Progesterone, and Quinidine
چکیده انگلیسی

ABSTRACTMolecular relaxation in ultraviscous melt and glassy states of aspirin, ibuprofen, progesterone, and quinidine has been studied by dielectric spectroscopy. The asymmetric relaxation spectra is characterized by the Kohlrausch distribution parameter of 0.46 ± 0.02 for aspirin to 0.67 ± 0.02 for progesterone. The dielectric relaxation time varies with the temperature, T, according to the Vogel–Fulcher–Tammann Equation, log10(τ0) = AVFT + [BVFT/(T − T0)], where AVFT, BVFT, and T0 are empirical constants. The extrapolated τ0 at calorimetric glass-softening temperature is close to the value expected. The equilibrium permittivity, ε0, is lowest for ibuprofen which indicates an antiparallel orientation of dipoles in its liquid's hydrogen-bonded structure. A decrease in ε0 with time shows that ultraviscous aspirin, progesterone, and quinidine begin to cold-crystallize at a relatively lower temperature than ibuprofen. ε0 of the cold-crystallized phases are, 4.7 for aspirin at 290 K, 2.55 for ibuprofen at 287 K, 2.6 for progesterone at 320 K, and 3.2 for quinidine at 375 K. It is argued that hydrogen-bonding, the Kohlrausch parameter, extent of localized motions and the long-range diffusion times all determine the physical and chemical stability of an amorphous pharmaceutical during storage.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Pharmaceutical Sciences - Volume 96, Issue 5, May 2007, Pages 1159–1175
نویسندگان
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